In principle I support the idea of a new railway track going north south in England increasing the capacity. The problem with the current proposal it's all about building an independent transport system not integrated with the current rail or other public transport systems.
The problems is as I see it so that they have new stations except in London and Manchester, I’ll come to London later. There's a new station in Nottingham in the middle of nowhere, but close to the Motorway. In Birmingham is not as a new station, if fact a very old one, Curzon Street, but that stopped being used for long distance trains in 1854 when New Street was opened. Because New Street was a better location and closer to the city centre! The new station will be close to Moor Street but will be about a ten minutes walk away from the main Birmingham station of New Street. So for most of us, including us from Malvern I doubt if it will quicker to use HS2 rather than the existing West coast main line trains. I suspect the same may also apply to the Nottingham and the rest of the East Midlands and Sheffield.
Does the speed have to be so fast? Looking a projected time savings the only place where this is significant is London to Manchester see wikipedia . So should it be such a fast line? Running slightly slower will save construction cost. Less tunnels etc. as the line can curve more, and will use less energy when it is running.
The problem with London is London, the current HS2 plans don't have any connection with HS1 and most importantly there are no plans to a direct trains from Birmingham to the continent. A lot the supporters of HS2 just see it as a way of getting to and from London. To rebalance the economy of the UK away from London, what is needed is better connection with places that are not London. If HS2 is to any use to the people of Birmingham and the West Midlands region there it must be direct trains from Birmingham to Paris and beyond. Without out these direct connections it will just suck more into London.